Hi again Dave,
I have never tried one on but I wouldn't be surprised if it weighed into the heavyweight division!
I do have a 12/6 doubleneck, although it is a mere Korean jobby and it is 'bloody heavy' to coin a phrase! Not overly so, but all the doublenecks I've ever played have been well into double figures lb-wise. Its the territory.
I'd advise a note from your chiropractor before you consider playing one for more than a few songs. That's no reason not to buy a 1275 of course! Just do the warm up exercises and work out a little first!
Its not a Gibson, so please pardon the pic, but here's my doubleneck. For the record it plays and sounds great, the build quality is good and upper fret access is amazing. Its a player, not a collectible!